Comparing Submit JSON to Jotform is like comparing apples to oranges. Both products handle form submissions, but the use cases between them are quite different.
Jotform is a "form builder" where Submit JSON is a "form backend".
Developers will generally choose Submit JSON, where non-technical folks will generally prefer a solution like Jotform.
Jotform is essentially a clone of Google Forms with some added features, integrations, and a much higher price tag.
If you're searching for the best form builder, our recommendation is Google Forms or Tally.
But if you'd like to maintain control over your UI and UX, or do something fancy like alert yourself when a new user subscribes to your SaaS, Submit JSON is the more appropriate (and affordable) choice for your project.